Range.deleteContents shouldn't throw HierarchyRequestError on doctype

Source/core/dom/Range.cpp

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Gunnstein Lye (gunnstein@netcom.no)
  * (C) 2000 Frederik Holljen (frederik.holljen@hig.no)
  * (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Motorola Mobility. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 444 matching lines @@
 }
 
 bool Range::boundaryPointsValid() const
 {
     TrackExceptionState exceptionState;
     return compareBoundaryPoints(m_start, m_end, exceptionState) <= 0 && !exceptionState.hadException();
 }
 
 void Range::deleteContents(ExceptionState& exceptionState)
 {
-    checkDeleteExtract(exceptionState);
-    if (exceptionState.hadException())
-        return;
+    ASSERT(boundaryPointsValid());
 
     {
         EventQueueScope eventQueueScope;
         processContents(DELETE_CONTENTS, exceptionState);
     }
 }
 
 bool Range::intersectsNode(Node* refNode, ExceptionState& exceptionState)
 {
     // http://developer.mozilla.org/en/docs/DOM:range.intersectsNode
@@ skipping 1232 matching lines @@
 
 void showTree(const blink::Range* range)
 {
     if (range && range->boundaryPointsValid()) {
         range->startContainer()->showTreeAndMark(range->startContainer(), "S", range->endContainer(), "E");
         fprintf(stderr, "start offset: %d, end offset: %d\n", range->startOffset(), range->endOffset());
     }
 }
 
 #endif